Rayon / Viscose
Regenerated cellulose
What it is
An absorbent fiber made from wood pulp, used in most tampons, often blended with cotton. It absorbs more per gram than cotton, which is exactly why it became standard and why it carries a specific history.
In this product: Absorbent core fiber.
Dose & route, what actually matters
TSS risk rises with absorbency higher than your flow needs and with leaving a tampon in too long, not simply with using rayon. Use the lowest absorbency that works, change it on schedule, and the risk is very low (roughly 0.07 cases per 100,000 people who menstruate per year).
EUROPEAN UNION
No EU prohibition; bleaching is regulated toward chlorine-free processing.
UNITED STATES
Since 1990 the FDA standardizes tampon absorbency labels (light to super-plus) so users can pick the lowest effective absorbency; TSS warnings have been required since 1982.
The evidence
The 1980 toxic shock epidemic peaked at 814 reported cases and 38 deaths and was tied to high-absorbency synthetic-fiber tampons (notably P&G's withdrawn Rely); cases fell sharply after reformulation and absorbency standardization.
human · 1990 · source
Current US TSS rate is about 0.07 cases per 100,000 people who menstruate annually; today's viscose rayon is considered safe, with absorbency and wear time the operative risk variables.
review · 2024 · source
California Prop 65: Not listed.
How to avoid it
Use the lowest absorbency that handles your flow, change tampons every 4 to 8 hours, and consider 100% organic cotton if you want to skip wood-pulp rayon entirely.
Where it hides
Editorial analysis of publicly available regulatory and peer-reviewed sources. Not medical advice. We name our evidence and link it, including when an ingredient is fine.